Method for curling highly crystalline synthetic fibers and filaments



Dec. Z2, 1959 L. F. RoKosZ METHOD FOR CURLING HIGHLY CRYSTALLINESYNTHETIC FIBERS AND FILAMENTS Filed Feb. 23. 195e TTNEYS United StatesPatent IVIETHOD FOR CURLING HIGHLY CRYSTALLINE SYNTHETIC FIBERS ANDFILAMENTS Leo F. Rokosz, Linwood, Mich., assignor to The Dow ChemicalCompany, Midland, Mich., a corporation of Delaware Application February23, 1956, Serial No. 567,291

Claims. (Cl. 2S-72) This invention relates to an improved method forproducing a curliness or crinkle in synthetic fibers and filamentscomprised of highly crystalline polymeric or resin ous thermoplasticmaterials.

In order to facilitate their being more advantageously processed intospun yarns and the like, and for other purposes, it is desirable toprovide a wool-resembling curliness or crinkle for synthetic fibers andfilaments. Pinching gears, opposed tinted or serrated roller or beltsystems and various types of stuffing box crimpers are employedfrequently for this purpose. Their utilization, however, may tend tohave a deleterious inuence on the physical properties of the fiber. Thealso involve additional mechanical processing operations in themanufacture of the fiber. It would be beneficial, therefore, to avoidmechanical crimping operations for purposes of curling or crinklingsynthetic fibers and filaments.

Advantageously, this may be accomplished with certain types of highlycrystalline synthetic fibers and filaments, particularly with thosewhich may be obtained when coagulable latex emulsions of highlycrystalline, fiberforming, synthetic polymeric materials, such as sarancopolymers containing copolymerized vinylidene chloride, are employedfor forming the filamentary material.

According to the invention, a highly crystalline synthetic fiber and thelike may be provided with a permanent, wool-resembling crimp bydirectionally heating the fiber while it is in a relaxed condition tounilaterally differentially amorphize it cross-sectionally; tensioningthe differentially amorphized, relaxed ber so as to preferentiallyelongate it in its more amorphous cross-sectional regions, stretchingsaid fiber to a completely oriented condition; and relaxing saidoriented fiber.

After its orientation, the relaxing fiber assumes a permanent curlinessor crinkled condition due to the differential amounts or degrees ofrelaxation which are experienced by its opposing, differentiallyamorphized sides or cross-sectional regions. The curliness which maythus be imparted to the fiber equals or exceeds the crimp that isobtainable for many fibers for conventional mechanical crimping means.The pitch of the crimp or degree of curliness which may be imparted to afiber having a given thickness by practice of the invention isadvantageously variable with changes in the conditions of operation. Amore drastic differential amorphization, for example, or more pronouncedpreferential elongation or attenuation of the differentially amorphizedfiber or greater degrees of orientation, or any combination of theseinfiuences, usually effect a greater degree of curliness or a finercrimp in the fiber.

Advantageously, as is schematically illustrated in the accompanyingdrawing, the method of the invention may be practiced by placing thefiber in a relaxed condition on a heated, non-adherescent surface tounilaterally differentially amorphize it cross-sectionally; drawing theheated, differentially amorphized, relaxed fiber from said surface so asto preferentially elongate it in its more amorphous cross-sectionalregions; and subsequently orienting and relaxing said liber to producethe desired curliness therein.

Beneficially, uninterrupted or endless lengths of the fiber may beemployed and the fiber may be curled and the method may be practiced ina continuous manner by employing a traveling, heated, non-adherescentsurface, which conveniently may be in the form of an endless belt or thelike, upon and from which an uninterrupted length of fiber iscontinuously placed and withdrawn to subsequently be continuouslyoriented and relaxed. The curled fiber product may be stapled forsubsequent mechanical spinning operations or it may be otherwise treatedand employed as a permanently crimped filamentary article.

Various materials which are not susceptible to sticking or coalescencewith the amorphized fiber may be ernployed for providing the heated,non-adherescent surface. Advantageously, a silicone rubber material or asurface treated with a repellent silicone material may be utilized,although in some cases polytetrafiuoroethylene and like materials mayform satisfactory surfaces. The surface may be heated by any desiredmeans and in any desired manner. It may frequently be convenient anddesirable to employ infra-red heating means for the purpose of heatingthe non-adherescent surface.

It is usually advantageous to curl a freshly formed filamentary materialby the method of the invention. ln certain instances, a partial orcomplete drying of a freshly formed, wet fiber may be accomplishedsimultaneously with its differential amorphization on the heatedsurface. If it is desired, however, the ber may be obtained from anysuitable supply of oriented material. Hollow fibers, such as those whichmay be obtained by spinning through annular orifices and by other knownprocedures, are often especially well suited for being effectivelycurled according to the method of the invention. This is due to theirusually more pronounced capability for being more drasticallycross-sectionally, differentially amor phized when they are unilaterallydirectionally heated.

While fibers from any highly crystalline polymeric or resinousfiber-forming material may ordinarily be curled by the present method,the invention is particularly adapted to be practiced with fibers whichare comprised of the normally highly crystalline satan copolymers. It isespecially advantageous to employ bers prepared from the highlycrystalline saran copolymers of vinylidene chloride and acrylonitrile,particularly those which contain at least about percent by weight ofvinylidene chloride polymerized in the copolymer molecule. When saranfibers are curled, it is advantageous for their differentialamorphization to be accomplished on a non-adherescent surface which isheated to a temperature between about and 175 C. and, moreadvantageously, particularly when Saran copolymers of vinylidenechloride and acrylonitrile are employed, between about and 175 C. Theformation of such fibers as well as their orientation and relaxation inthe practice of the invention may advantageously be accomplishedaccording to conventional techniques for such purposes.

Extremely effective crimping results may be obtained when the method ofthe invention is utilized to curl fibers from saran copolymers ofvinylidene chloride and acrylonitrile which contain about 97 percent byweight of vinylidene chloride polymerized in the copolymer molecule.Fine fibers of such copolymers may', for example, be readily obtained bypractice of the invention having a 2O to 35 percent permanent crimpinduced with from 4 to 12 curls and more per inch in the fiber product.

What is claimed is:

l. Method for curling highly crystalline synthetic fibers of a normallyhighly crystalline saran copolymer to provide them with a permanentcrimp which comprises directionally heating the ber while it is in arelaxed condition to unilaterally differentially amorphize itCrosssectionally; tensioning the differentially amorphized, relaxed berso as to preferentially elongate it in its more amorphouscross-sectional regions without substantially orienting said fiber;stretching said fiber to a completely oriented condition; and relaxingsaid oriented fiber.

2. Method for curling highly crystalline synthetic bers of a normallyhighly crystalline saran copolymer to provide them with a permanentcrimp which comprises placing the iiber in a relaxed condition on aheated, nonadherescent surface to unilaterally diierentially a'morphizeit cross-sectionally; drawing the heated, diiferentially arnorphized,relaxed ber from said surface so as to preferentially elongate it in itsmore amorphous crosssectional regions without substantially orientingsaid fiber; stretching said fiber to a completely oriented condition;and relaxing said oriented fiber.

3. The method of claim 2 wherein said fiber is in the form of anuninterrupted, endless length which is continuously placed on atraveling non-adherescent surface and wherein the steps of drawing saidliber from the surface to preferentially elongate it; stretching saidliber t orient it and relaxing the oriented ber are continuouslyperformed.

4. The method of claim 2 wherein the non-adherescent surface iscomprised of a silicone material.

5. The method of claim 2 wherein the non-adherescent surface is heatedby infra-red heating means.

6. The method of claim 2 wherein said liber is a hollow fiber.

7. The method of claim 2 wherein the non-adherescerit surface is heatedto a temperature between about 160 and 175 C. to dilerentially amorphizesaid fiber.

8. The method of claim 2 wherein said fiber is comprised of a sarancopolymer of vinylidene chloride and acrylonitrile containing at leastabout percent by weight of vinyiidene chloride polymerized in thecopolymer molecule and wherein the non-adherescent surface is heated toa temperature between about and 175 C. to differentially amorphize saidber.

9. The method of claim 2 wherein said fiber is comprised of a Sarancopolymer of vinylidene chloride and acrylonitrile containing about 97percent by weight of vinylidene chloride polymerized in the copolymermolecule and wherein the nonadherescent surface is heated to atemperature between about and 175 C. to differentially amorphize saidfiber.

10. A method in accordance with the method of claim 9 wherein said iiberis a hollow ber.

References Cited in the file of this patent UNITED STATES PATENTS2,242,988 Averns May 20, 1941 2,333,279 Truesdail Nov. 2, 1943 2,338,978Shepherd Jan. l1, 1944 2,344,511 Harder Mar. 2l, 1944 2,377,810 RobbinsJune 5, 1945 2,399,259 Taylor Apr. 30, 1946 2,542,973 Abernethy Feb. 27,1951 2,543,027 Jones Feb. 27, 1951 2,602,964 Sisson July 15, 19522,708,813 Bourgeaux May 24, 1955 2,730,758 Morrell et al. Jan. 17, 19562,758,908 Kolb Aug. 14, 1956 2,764,468 Hare Sept. 25, 1956

1. METHOD FOR CURLING HIGHLY CRYSTALLINE SYNTHETIC FIBERS OF A NORMALLYHIGH CRYSTALLINE SARAN COPOLYMER TO PROVIDE THEM WITH A PERMANENT CRIMPWHICH COMPRISES DIRECTIONALLY HEATING THE FIBER WHILE IT IS IN A RELAXEDCONDITION TO UNILATERALLY DIFFERENTIALLY AMORPHIZE IT CROSSSECTIONALLY;TENSIONING THE DIFFERENTIALLY AMORPHIZED, RELAXED FIBER SO AS TOPREFERENTIALLY ELONGATE IT IN ITS MORE